Characterizing Populations and Reproduction Strategies Flashcards
Population
All members of a single species living in a specific area at the same time
population size
Number of individuals
Population Density
Number of individuals living in a given area (Individuals/area^2)
Random, Uniform, Clustered
Birthrate or natality
Number of live births added annually per 1000 individuals
Crude Birth Rate = (No. of live births in a year/Population size) x 1000
Deathrate or mortality
Number of deaths added annually per 1000 individuals
Crude Death Rate = (No. of deaths in a year/Population size) x 1000
natural Growth rate
(%) = Birthrate - Deathrate
Doubling time
(Years) = 70/Growth rate (%)
Immigration
Movement of individuals into a population
Emigration
Movement of individuals out of a population
Total growth rate (%)
Total growth rate (%) = (crude Birthrate + immigration) - (crude death rate + emigration)
Calculating population size using growth rate
P(t) = P(0)e^rt
P(t) = Population at the time t
P(0) = initial population at time 0
e = eulers number
r = growth rate
t = length of time
Sex ratio
Number of males with respect to number of females
Number of males/number of females = Sex Ratio
Age distribution
- Pre-reproductive juveniles
- Reproductive adults
- Post-reproductive adults
Types of growth
Exponential (J-curve)
Logistic (S-curve)
Exponential Growth Rate
An increase in individuals per unit of time “Growth with no limit”
dN/dt = rN
N = number of individuals
r = rate of growth
Carrying Capacity
The maximum population size of a biological species that can be sustained by that specific environment
Logistic Growth Rate
Changes in growth over time
Growth slows when approaching carrying capacity
dN/dt = rN((K - N)/K)
N = number of individuals
r = rate of growth
K = carrying capacity
Limiting Factors
Factors that prevent the further increase of the population
Determine an ecosystem’s carrying capacity
Environmental Resistance
The totality of all limiting factors
Factors affecting growth
Density-dependent factors
1. External Factors
2. Internal Fators
Density-independent factors
External Factors
habitat quality, food availability, interactions
Internal Factors
Slow growth and maturity, body size, metabolism, hormonal status
Density-dependent factors
Effect intensifies with increase in population size
Density-independent population factors
Population affected no matter what size (often abiotic)
Such as climate extremes, seasonal cycles, pollutants in the environment, fires
R-strategies
- Usually small
- Highly reproductive rate
- High mortality
- Ignored offspring
Depend on high rate of reproduction and growth (r)
- may overshoot carrying capacity and experience population crashes
- too many young, few will survive
K-strategies
- Tend to be large
- Live long lives, mature slowly
- Care for offspring
- Low reproductive rate
- Low mortality
Adapted for slower growth conditions near carrying capacity (K)
